The invention relates to a device for the temporary storage and metered supply of fuel vapor from a fuel tank system to a combustion engine, wherein the system includes a fuel tank having a free space therein, a deaeration pipe connecting the free space to the surrounding atmosphere, and a storage chamber having an absorptive element incorporated in the deaeration pipe. The device is located between the storage chamber and the engine, and includes an electromagnetic stop valve, a control chamber between the stop valve and the engine, and auxiliary means in the control chamber to change the metering capacity of the stop valve.
Such a device is known from the DE-OS 35 19 292. It is the purpose of this device to avoid an escaping of the fuel vapors which are constantly present in the free space of the fuel tank into the atmosphere. The device makes use of a special deaeration pipe which is disposed between the free space and the atmosphere and in which is incorporated a storage chamber having an absorptive element. The latter mostly is a permeable body of activated carbon which is suited to temporary store a significant amount of volatile fuel. To regenerate the absorptive element fresh air is sucked through the latter during normal operation of the combustion engine; to do so a a pipe is used connecting the storage chamber with the intake pipe of the combustion engine. However, it must be taken into account that at a low rotational speed of the combustion engine and/or at a particularly high degree of saturation of the absorptive element, the fuel/air mixture sucked in by the combustion engine can possibly become "overrich", which can result in malfunctions. Therefore, the pipe can be closed by an electromagnetic stop valve which can be adjusted with regard to the metering capacity by external sensors, on the one hand, and by a subatmospheric pressure in the pipe which affects the closing link, on the other hand.